Systems are known which are adapted for use to transfer desired volumes of liquid chemicals of the types applied to the earth or plants from supplies of the liquid chemicals to containers. Such systems may be as simple as a pail into which a predetermined volume of the liquid is poured and from which the liquid is poured into the container which may contain water which dilutes the chemical and which is applied with the liquid in a predetermined volume or amount per unit area onto the earth and/or plants. A more sophisticated system currently sold by Great Planes Industries, Incorporated, Wichita, Kans., includes a pump operable to transferring the liquid through a supply line from a supply of the liquid to a container, and an impeller in the transfer line that is operated by liquid flowing through the supply line and in turn operates a counter included in an electronic system associated with the impeller that counts the revolutions of the impeller. To operate the system, a user first transfers enough liquid by the pump and past the impeller to fill a container of a known volume (e.g., a 5 gallon pail), and then, using the electronic system, determines the volume of that liquid that passed the impeller during each rotation of the impeller and calibrates the electronic system so that each future revolution of the propeller that occurs in transferring a liquid will indicate that the same volume of liquid has passed the impeller. The calibrated system is then used to transfer a desired volume of the same liquid to a holding tank, the pumping system being manually stopped when the electronic system operated by the calibrated impeller indicates that the desired volume of liquid has been delivered. The delivered liquid is then typically mixed with other liquids (e.g., water), after which the mixture is sprayed onto a predetermined area or amount of earth and/or plants.
While either of these systems can be used successfully, both systems are easily misused so that the desired volume of liquid is not delivered, and both systems expose the user to the liquid more than is desired, particularly where the liquid is of the type that provides a high degree of danger to the user.